DOCSLIB.ORG

Solving Mixed-Integer Quadratic Programming Problems with IBM-CPLEX: a Progress Report

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Solving Mixed-Integer Quadratic Programming Problems with IBM-CPLEX: a Progress Report Proceedings of the Twenty-Sixth RAMP Symposium Hosei University, Tokyo, October 16-17, 2014 Solving Mixed-Integer Quadratic Programming problems with IBM-CPLEX: a progress report 1 2 3 Christian Bliek ú, Pierre Bonami †, and Andrea Lodi ‡ Abstract Mixed-Integer Quadratic Programming problems have a vast impact in both theory and practice of mathematical optimization. Classical algorithmic approaches, their implemen- tation within IBM-CPLEX and new algorithmic advances will be discussed. Keywords Quadratic Programming, branch and bound, convex programming, bound reduc- tion 1. Introduction We consider the general Mixed-Integer Quadratic Programming (MIQP) problem 1 T T min 2 x Qx + c x (1) Ax = b (2) xj Z j =1,...,p (3) œ l x u (4) Æ Æ n n where Q ◊ is a symmetric matrix. Note that constraints (4) are fundamental in the complex- ity sense because a striking result by Jeroslow [11] proves the undecidability of unbounded problems. The relevance of MIQP in Mathematical Optimization is twofold. On the one side, a number of applications arise in a practical setting starting from the most classical one in portfolio optimization, see, e.g., [4, 7, 17]. On the other side, MIQP has been clearly the first step for a methodological generalization of Mixed-Integer Linear Programming (MILP) to general Mixed-Integer Nonlinear Programming (MINLP). It is well known that MIQP is NP-hard, trivially because it contains MILP as a special case. However, it is important to notice that, differently from MILP, the source of complexity of MIQP is not restricted to the integrality requirement on (some of) the variables (3). In fact, the (continuous) Quadratic Programming (QP) special case (i.e., p =0) is, in general, NP-hard as well. Let G =(N,E) be a graph and Q be the incidence matrix of G. The 1 CPLEX Optimization, IBM France, 1681-HB2 Route des Dolines 06560 Valbonne, France 2 CPLEX Optimization, IBM Spain, Sta. Hortensia 26-28, 28002 - Madrid (M), Spain 3 DEI, University of Bologna, and IBM-Unibo Center of Excellence in Mathematical Optimization, Viale Risorgimento 2, 40136, Bologna, Italy E-mail address: [email protected] ú E-mail address: [email protected] † E-mail address: [email protected] ‡ － 171 － The Twenty-Sixth RAMP Symposium optimal value of 1 n min xT Qx : x =1,x 0 Y2 j Ø Z ] jÿ=1 ^ is 1 1 1 , where ‰(G) is the[ clique number of G [14], which\ is well-known to be NP-hard 2 ≠ ‰(G) to compute.1 2 Therefore, we will distinguish between the case in which the relaxation obtained by drop- ping the integrality requirements (3) (if any) is convex (thus, solvable in polynomial time), and that in which it is nonconvex. Roughly speaking, convex MIQPs are currently solved by heavily relying on MILP techniques by either replacing in the classical branch-and-bound scheme the Linear Programming (LP) solver with a QP solver, or solving MILPs as subprob- lems. Instead, nonconvex MIQPs require somehow more sophisticated techniques, namely Global Optimization (GO). An intermediate case between these two is the one where Q is not convex but MIQP can easily be reformulated as a convex MIQP. This is true for example when all variables are constrained to be 0-1, or more generally when all products are between a 0-1 variable and a bounded variable. In this short paper we review the IBM-CPLEX evolution in solving QPs and MIQPs with special emphasis on nonconvex MIQPs because the capability of solving them to proven op- timality has been added into the solver very recently. Schematically, Table 1 below outlines a brief history of MIQP within CPLEX, where B&B stands for branch and bound. We remind the reader that a QP is convex if and only if the matrix Q is positive semidefinite. class pQalgorithm V. (Year) convex QP 0 0 barrier 4.0 (1995) ≤ – – – QP simplex 8.0 (2002) convex MIQP > 0 0 B&B 8.0 (2002) ≤ nonconvex QP 0 0 barrier (local) 12.3 (2011) ”≤ – – – spatial B&B (global) 12.6 (2013) nonconvex MIQP > 0 0 spatial B&B (global) 12.6 (2013) ”≤ Table 1 History of MIQP within CPLEX. The paper is organized as follows. In Section 2 we briefly discuss the classical algorithms for convex MIQPs and some specific implementation choices that are peculiar of CPLEX. In Section 3 we move to the nonconvex MIQP case and we present the current status of implementation of solution techniques for them. Both Sections 2 and 3 end with some com- putational experiments giving a snapshot of the current performance of CPLEX on MIQPs. Since the algorithmic treatment of 0-1 nonconvex MIQPs is more similar to that of convex MIQPs than nonconvex MIQPs, we will review them as part of the section on convex MIQPs. Finally, in Section 4 we draw some conclusions. － 172 － The Twenty-Sixth RAMP Symposium 2. Convex MIQPs The solution of convex MINLPs has reached in the last decade a rather stable and mature algorithmic technology, see, e.g., Bonami et al. [6]. Essentially, the two corner stones of algorithms and software are Nonlinear Programming (NLP)-based branch-and-bound [10] and Outer Approximation (OA) [8] algorithms. Although the NLP-based branch and bound is the only relevant for CPLEX (see discussion at the end of the section) for the special case of (convex) MIQPs, we review the OA as well. This is because the most standard trick in MINLP is to add a variable – R, replace the original objective function with œ “min –” and add the constraint f(x) –. Of course, this could be done for MIQPs as 1 T T Æ well (f(x)= 2 x Qx + c x in that case), thus transforming the problem in a convex Mixed- Integer Quadratically-Constrained Programming (MIQCP) problem and sometimes it does make sense in practice [9]. The NLP-based branch and bound is a straightforward generalization of the main enu- merative algorithm for MILP. The main difference is that an NLP, a QP in our special case, is solved at every node of the branch-and-bound tree to provide a valid lower bound, in- stead of an LP problem. The other main components of the MILP scheme remain the same: branching on the integer constrained variables, and pruning nodes based on • infeasibility: the node relaxation is infeasible, • bound: the node lower bound value is not smaller than the incumbent solution value, and • integer feasibility: the node relaxation admits an integer solution. The main source of inefficiency of this straightforward extension is, in general convex MINLP, the difficulty of warm starting NLP solvers, i.e., reusing the information on the solution of a relaxation from a node to another. However, for the convex MIQP case this issue is relatively under control when the QP simplex is used to solve the node relaxation. The basic idea of the OA decomposition is to take first-order approximations of constraints at different points and build an MILP equivalent to the initial MINLP. This corresponds for a nonlinear function g(x) and for a set K of its points xk,k K to write the constraints œ g(xk)+ g(xk)T (x xk) 0.k K (5) Ò ≠ Æ œ This basic idea is illustrated in Figure 1. It is easy to see that the MILP constructed through an initial set of linearization points is a relaxation of the original convex MINLP. Then, if solved to optimality, it provides a valid lower bound value for the original problem and a solution xˆ such that xˆj Z,j =1,...,p. œ However, this solution might be NLP infeasible (because of the first-order approximation used) and the NLP(ˆx) obtained by fixing the integer component of the original problem (xj =ˆxj,j =1,...,p) is solved. If NLP(ˆx) is feasible, then it in turn provides an upper bound value. Otherwise, general-purpose NLP software will typically return a weighted min- K +1 imization of the violation of the constraints. In both cases, a new point x| | can be added － 173 － The Twenty-Sixth RAMP Symposium Outer Approximation [Duran and Grossmann, 1986] min cT x s.t. g (x) 0 i = 1,...,m, i ≤ xj Z j = 1,...,p. ∈ Figure 1 The Outer Approximation MILP equivalent. Idea: Take first-order approximations of constraints at different points to the set K, and the methodand is iterated build by an applying equivalent first-order MILP. approximation to it, thus en- hancing the quality of the MILP equivalent. Duran and Grossman [8] show that the iterative T scheme converges to the optimal solutionmin c valuex of the original problem in a finite number of steps, provided the nonlinear functionss.t. are convex and continuously differentiable, and that a constraint qualification holds for each point xk,k K. g (x k )+ g (xœk )T (x x k ) 0 i = 1,...,m, k = 1,...,K The OA algorithm outlined abovei requires∇ solvingi one MILP− at≤ each iteration. This can be rather time consuming if the initialxj Z MILP does not provide a good approximation of the j = 1,...,p. ∈ original problem. However, the OA can be embedded in a single tree search [15, 6, 1]. Namely, start solving the same initial MILP by branch and bound and at each integer feasible node: 12 Andrea Lodi, University of Bologna (i) Solve NLP(ˆx), and enrich the set of linearization points, (ii) Resolve the LP relaxation of the node with the new fist-order constraints, and (iii) Repeat as long as node is integer feasible. Of course, no pruning is allowed by integer feasibility.
Load more

Recommended publications
  • Chapter 8 Constrained Optimization 2: Sequential Quadratic Programming, Interior Point and Generalized Reduced Gradient Methods
    Chapter 8: Constrained Optimization 2 CHAPTER 8 CONSTRAINED OPTIMIZATION 2: SEQUENTIAL QUADRATIC PROGRAMMING, INTERIOR POINT AND GENERALIZED REDUCED GRADIENT METHODS 8.1 Introduction In the previous chapter we examined the necessary and sufficient conditions for a constrained optimum. We did not, however, discuss any algorithms for constrained optimization. That is the purpose of this chapter. The three algorithms we will study are three of the most common. Sequential Quadratic Programming (SQP) is a very popular algorithm because of its fast convergence properties. It is available in MATLAB and is widely used. The Interior Point (IP) algorithm has grown in popularity the past 15 years and recently became the default algorithm in MATLAB. It is particularly useful for solving large-scale problems. The Generalized Reduced Gradient method (GRG) has been shown to be effective on highly nonlinear engineering problems and is the algorithm used in Excel. SQP and IP share a common background. Both of these algorithms apply the Newton- Raphson (NR) technique for solving nonlinear equations to the KKT equations for a modified version of the problem. Thus we will begin with a review of the NR method. 8.2 The Newton-Raphson Method for Solving Nonlinear Equations Before we get to the algorithms, there is some background we need to cover first. This includes reviewing the Newton-Raphson (NR) method for solving sets of nonlinear equations. 8.2.1 One equation with One Unknown The NR method is used to find the solution to sets of nonlinear equations. For example, suppose we wish to find the solution to the equation: xe+=2 x We cannot solve for x directly.
    [Show full text]
  • Quadratic Programming GIAN Short Course on Optimization: Applications, Algorithms, and Computation
    Quadratic Programming GIAN Short Course on Optimization: Applications, Algorithms, and Computation Sven Leyffer Argonne National Laboratory September 12-24, 2016 Outline 1 Introduction to Quadratic Programming Applications of QP in Portfolio Selection Applications of QP in Machine Learning 2 Active-Set Method for Quadratic Programming Equality-Constrained QPs General Quadratic Programs 3 Methods for Solving EQPs Generalized Elimination for EQPs Lagrangian Methods for EQPs 2 / 36 Introduction to Quadratic Programming Quadratic Program (QP) minimize 1 xT Gx + g T x x 2 T subject to ai x = bi i 2 E T ai x ≥ bi i 2 I; where n×n G 2 R is a symmetric matrix ... can reformulate QP to have a symmetric Hessian E and I sets of equality/inequality constraints Quadratic Program (QP) Like LPs, can be solved in finite number of steps Important class of problems: Many applications, e.g. quadratic assignment problem Main computational component of SQP: Sequential Quadratic Programming for nonlinear optimization 3 / 36 Introduction to Quadratic Programming Quadratic Program (QP) minimize 1 xT Gx + g T x x 2 T subject to ai x = bi i 2 E T ai x ≥ bi i 2 I; No assumption on eigenvalues of G If G 0 positive semi-definite, then QP is convex ) can find global minimum (if it exists) If G indefinite, then QP may be globally solvable, or not: If AE full rank, then 9ZE null-space basis Convex, if \reduced Hessian" positive semi-definite: T T ZE GZE 0; where ZE AE = 0 then globally solvable ... eliminate some variables using the equations 4 / 36 Introduction to Quadratic Programming Quadratic Program (QP) minimize 1 xT Gx + g T x x 2 T subject to ai x = bi i 2 E T ai x ≥ bi i 2 I; Feasible set may be empty ..
    [Show full text]
  • Gauss-Newton SQP
    TEMPO Spring School: Theory and Numerics for Nonlinear Model Predictive Control Exercise 3: Gauss-Newton SQP J. Andersson M. Diehl J. Rawlings M. Zanon University of Freiburg, March 27, 2015 Gauss-Newton sequential quadratic programming (SQP) In the exercises so far, we solved the NLPs with IPOPT. IPOPT is a popular open-source primal- dual interior point code employing so-called filter line-search to ensure global convergence. Other NLP solvers that can be used from CasADi include SNOPT, WORHP and KNITRO. In the following, we will write our own simple NLP solver implementing sequential quadratic programming (SQP). (0) (0) Starting from a given initial guess for the primal and dual variables (x ; λg ), SQP solves the NLP by iteratively computing local convex quadratic approximations of the NLP at the (k) (k) current iterate (x ; λg ) and solving them by using a quadratic programming (QP) solver. For an NLP of the form: minimize f(x) x (1) subject to x ≤ x ≤ x; g ≤ g(x) ≤ g; these quadratic approximations take the form: 1 | 2 (k) (k) (k) (k) | minimize ∆x rxL(x ; λg ; λx ) ∆x + rxf(x ) ∆x ∆x 2 subject to x − x(k) ≤ ∆x ≤ x − x(k); (2) @g g − g(x(k)) ≤ (x(k)) ∆x ≤ g − g(x(k)); @x | | where L(x; λg; λx) = f(x) + λg g(x) + λx x is the so-called Lagrangian function. By solving this (k) (k+1) (k) (k+1) QP, we get the (primal) step ∆x := x − x as well as the Lagrange multipliers λg (k+1) and λx .
    [Show full text]
  • Implementing Customized Pivot Rules in COIN-OR's CLP with Python
    Cahier du GERAD G-2012-07 Customizing the Solution Process of COIN-OR's Linear Solvers with Python Mehdi Towhidi1;2 and Dominique Orban1;2 ? 1 Department of Mathematics and Industrial Engineering, Ecole´ Polytechnique, Montr´eal,QC, Canada. 2 GERAD, Montr´eal,QC, Canada. [email protected], [email protected] Abstract. Implementations of the Simplex method differ only in very specific aspects such as the pivot rule. Similarly, most relaxation methods for mixed-integer programming differ only in the type of cuts and the exploration of the search tree. Implementing instances of those frame- works would therefore be more efficient if linear and mixed-integer pro- gramming solvers let users customize such aspects easily. We provide a scripting mechanism to easily implement and experiment with pivot rules for the Simplex method by building upon COIN-OR's open-source linear programming package CLP. Our mechanism enables users to implement pivot rules in the Python scripting language without explicitly interact- ing with the underlying C++ layers of CLP. In the same manner, it allows users to customize the solution process while solving mixed-integer linear programs using the CBC and CGL COIN-OR packages. The Cython pro- gramming language ensures communication between Python and COIN- OR libraries and activates user-defined customizations as callbacks. For illustration, we provide an implementation of a well-known pivot rule as well as the positive edge rule|a new rule that is particularly efficient on degenerate problems, and demonstrate how to customize branch-and-cut node selection in the solution of a mixed-integer program.
    [Show full text]
  • A Sequential Quadratic Programming Algorithm with an Additional Equality Constrained Phase
    A Sequential Quadratic Programming Algorithm with an Additional Equality Constrained Phase Jos´eLuis Morales∗ Jorge Nocedal † Yuchen Wu† December 28, 2008 Abstract A sequential quadratic programming (SQP) method is presented that aims to over- come some of the drawbacks of contemporary SQP methods. It avoids the difficulties associated with indefinite quadratic programming subproblems by defining this sub- problem to be always convex. The novel feature of the approach is the addition of an equality constrained phase that promotes fast convergence and improves performance in the presence of ill conditioning. This equality constrained phase uses exact second order information and can be implemented using either a direct solve or an iterative method. The paper studies the global and local convergence properties of the new algorithm and presents a set of numerical experiments to illustrate its practical performance. 1 Introduction Sequential quadratic programming (SQP) methods are very effective techniques for solv- ing small, medium-size and certain classes of large-scale nonlinear programming problems. They are often preferable to interior-point methods when a sequence of related problems must be solved (as in branch and bound methods) and more generally, when a good estimate of the solution is available. Some SQP methods employ convex quadratic programming sub- problems for the step computation (typically using quasi-Newton Hessian approximations) while other variants define the Hessian of the SQP model using second derivative informa- tion, which can lead to nonconvex quadratic subproblems; see [27, 1] for surveys on SQP methods. ∗Departamento de Matem´aticas, Instituto Tecnol´ogico Aut´onomode M´exico, M´exico. This author was supported by Asociaci´onMexicana de Cultura AC and CONACyT-NSF grant J110.388/2006.
    [Show full text]
  • A Parallel Quadratic Programming Algorithm for Model Predictive Control
    MITSUBISHI ELECTRIC RESEARCH LABORATORIES http://www.merl.com A Parallel Quadratic Programming Algorithm for Model Predictive Control Brand, M.; Shilpiekandula, V.; Yao, C.; Bortoff, S.A. TR2011-056 August 2011 Abstract In this paper, an iterative multiplicative algorithm is proposed for the fast solution of quadratic programming (QP) problems that arise in the real-time implementation of Model Predictive Control (MPC). The proposed algorithm–Parallel Quadratic Programming (PQP)–is amenable to fine-grained parallelization. Conditions on the convergence of the PQP algorithm are given and proved. Due to its extreme simplicity, even serial implementations offer considerable speed advantages. To demonstrate, PQP is applied to several simulation examples, including a stand- alone QP problem and two MPC examples. When implemented in MATLAB using single-thread computations, numerical simulations of PQP demonstrate a 5 - 10x speed-up compared to the MATLAB active-set based QP solver quadprog. A parallel implementation would offer a further speed-up, linear in the number of parallel processors. World Congress of the International Federation of Automatic Control (IFAC) This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc.
    [Show full text]
  • 1 Linear Programming
    ORF 523 Lecture 9 Princeton University Instructor: A.A. Ahmadi Scribe: G. Hall Any typos should be emailed to a a [email protected]. In this lecture, we see some of the most well-known classes of convex optimization problems and some of their applications. These include: • Linear Programming (LP) • (Convex) Quadratic Programming (QP) • (Convex) Quadratically Constrained Quadratic Programming (QCQP) • Second Order Cone Programming (SOCP) • Semidefinite Programming (SDP) 1 Linear Programming Definition 1. A linear program (LP) is the problem of optimizing a linear function over a polyhedron: min cT x T s.t. ai x ≤ bi; i = 1; : : : ; m; or written more compactly as min cT x s.t. Ax ≤ b; for some A 2 Rm×n; b 2 Rm: We'll be very brief on our discussion of LPs since this is the central topic of ORF 522. It suffices to say that LPs probably still take the top spot in terms of ubiquity of applications. Here are a few examples: • A variety of problems in production planning and scheduling 1 • Exact formulation of several important combinatorial optimization problems (e.g., min-cut, shortest path, bipartite matching) • Relaxations for all 0/1 combinatorial programs • Subroutines of branch-and-bound algorithms for integer programming • Relaxations for cardinality constrained (compressed sensing type) optimization prob- lems • Computing Nash equilibria in zero-sum games • ::: 2 Quadratic Programming Definition 2. A quadratic program (QP) is an optimization problem with a quadratic ob- jective and linear constraints min xT Qx + qT x + c x s.t. Ax ≤ b: Here, we have Q 2 Sn×n, q 2 Rn; c 2 R;A 2 Rm×n; b 2 Rm: The difficulty of this problem changes drastically depending on whether Q is positive semidef- inite (psd) or not.
    [Show full text]
  • Practical Implementation of the Active Set Method for Support Vector Machine Training with Semi-Definite Kernels
    PRACTICAL IMPLEMENTATION OF THE ACTIVE SET METHOD FOR SUPPORT VECTOR MACHINE TRAINING WITH SEMI-DEFINITE KERNELS by CHRISTOPHER GARY SENTELLE B.S. of Electrical Engineering University of Nebraska-Lincoln, 1993 M.S. of Electrical Engineering University of Nebraska-Lincoln, 1995 A dissertation submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in the Department of Electrical Engineering and Computer Science in the College of Engineering and Computer Science at the University of Central Florida Orlando, Florida Spring Term 2014 Major Professor: Michael Georgiopoulos c 2014 Christopher Sentelle ii ABSTRACT The Support Vector Machine (SVM) is a popular binary classification model due to its superior generalization performance, relative ease-of-use, and applicability of kernel methods. SVM train- ing entails solving an associated quadratic programming (QP) that presents significant challenges in terms of speed and memory constraints for very large datasets; therefore, research on numer- ical optimization techniques tailored to SVM training is vast. Slow training times are especially of concern when one considers that re-training is often necessary at several values of the models regularization parameter, C, as well as associated kernel parameters. The active set method is suitable for solving SVM problem and is in general ideal when the Hessian is dense and the solution is sparse–the case for the `1-loss SVM formulation. There has recently been renewed interest in the active set method as a technique for exploring the entire SVM regular- ization path, which has been shown to solve the SVM solution at all points along the regularization path (all values of C) in not much more time than it takes, on average, to perform training at a sin- gle value of C with traditional methods.
    [Show full text]
  • Treatment of Degeneracy in Linear and Quadratic Programming
    UNIVERSITE´ DE MONTREAL´ TREATMENT OF DEGENERACY IN LINEAR AND QUADRATIC PROGRAMMING MEHDI TOWHIDI DEPARTEMENT´ DE MATHEMATIQUES´ ET DE GENIE´ INDUSTRIEL ECOLE´ POLYTECHNIQUE DE MONTREAL´ THESE` PRESENT´ EE´ EN VUE DE L'OBTENTION DU DIPLOME^ DE PHILOSOPHIÆ DOCTOR (MATHEMATIQUES´ DE L'INGENIEUR)´ AVRIL 2013 c Mehdi Towhidi, 2013. UNIVERSITE´ DE MONTREAL´ ECOLE´ POLYTECHNIQUE DE MONTREAL´ Cette th`eseintitul´ee : TREATMENT OF DEGENERACY IN LINEAR AND QUADRATIC PROGRAMMING pr´esent´ee par : TOWHIDI Mehdi en vue de l'obtention du dipl^ome de : Philosophiæ Doctor a ´et´ed^ument accept´eepar le jury d'examen constitu´ede : M. EL HALLAOUI Issma¨ıl, Ph.D., pr´esident M. ORBAN Dominique, Doct. Sc., membre et directeur de recherche M. SOUMIS Fran¸cois, Ph.D., membre et codirecteur de recherche M. BASTIN Fabian, Doct., membre M. BIRBIL Ilker, Ph.D., membre iii To Maryam To Ahmad, Mehran, Nima, and Afsaneh iv ACKNOWLEDGEMENTS Over the past few years I have had the great opportunity to learn from and work with professor Dominique Orban. I would like to thank him sincerely for his exceptional support and patience. His influence on me goes beyond my academic life. I would like to deeply thank professor Fran¸cois Soumis who accepted me for the PhD in the first place, and has since provided me with his remarkable insight. I am extremely grateful to professor Koorush Ziarati for introducing me to the world of optimization and being the reason why I came to Montreal to pursue my dream. I am eternally indebted to my caring and supportive family ; my encouraging mother, Mehran ; my thoughtful brother, Nima ; my affectionate sister, Afsaneh ; and my inspiration of all time and father, Ahmad.
    [Show full text]
  • Solving Combinatorial Optimization Problems Via Reformulation and Adaptive Memory Metaheuristics
    Solving Combinatorial Optimization Problems via Reformulation and Adaptive Memory Metaheuristics Gary A. Kochenbergera, Fred Gloverb, Bahram Alidaeec and Cesar Regod a School of Business, University of Colorado at Denver. [email protected] b School of Business, University of Colorado at Denver. [email protected] c Hearin Center for Enterprise Science, University of Mississippi. [email protected] d Hearin Center for Enterprise Science, University of Mississippi. [email protected] ABSTRACT— Metaheuristics — general search procedures whose principles allow them to escape the trap of local optimality using heuristic designs — have been successfully employed to address a variety of important optimization problems over the past few years. Particular gains have been achieved in obtaining high quality solutions to problems that classical exact methods (which guarantee convergence) have found too complex to handle effectively. Typically a metaheuristic method is crafted to suit the particular characteristics of the problem at hand, exploiting to the extent possible the structure available to enable a fruitful and efficient search process. An alternative to this problem specific solution approach is a more general methodology that recasts a given problem into a common modeling format, permitting solutions to be derived by a common, rather than tailor-made, heuristic method. The optimization folklore strongly emphasizes the unproductive consequences of converting problems from a specific class to a more general representation, since the “domain-specific structure” of the original setting then becomes invisible and can not be exploited by a method for the more general problem representation. Nevertheless, there is a strong motivation to attempt such a conversion in many applications to avoid the necessity to develop a new method for each new class.
    [Show full text]
  • Solving Unconstrained 0-1 Polynomial Programs Through Quadratic Convex Reformulation Sourour Elloumi, Amélie Lambert, Arnaud Lazare
    Solving unconstrained 0-1 polynomial programs through quadratic convex reformulation Sourour Elloumi, Amélie Lambert, Arnaud Lazare To cite this version: Sourour Elloumi, Amélie Lambert, Arnaud Lazare. Solving unconstrained 0-1 polynomial programs through quadratic convex reformulation. 2019. hal-01872996v2 HAL Id: hal-01872996 https://hal.archives-ouvertes.fr/hal-01872996v2 Preprint submitted on 18 Jan 2019 (v2), last revised 12 Mar 2020 (v4) HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Solving unconstrained 0-1 polynomial programs through quadratic convex reformulation Sourour Elloumi1,2, Amélie Lambert2 and Arnaud Lazare1,2 1 UMA-ENSTA, 828 Boulevard des Maréchaux, 91120 Palaiseau, France {sourour.elloumi,arnaud.lazare}@ensta-paristech.fr 2 CEDRIC-Cnam, 292 rue saint Martin, F-75141 Paris Cedex 03, France [email protected] Abstract We propose an exact solution approach for the problem (P ) of min- imizing an unconstrained binary polynomial optimization problem. We call PQCR (Polynomial Quadratic Convex Reformulation) this three-phase method. The first phase consists in reformulating (P ) into a quadratic program (QP ). To that end, we recursively reduce the degree of (P ) to two, by use of the standard sub- stitution of the product of two variables by a new one.
    [Show full text]
  • Quadratic Programming Models in Strategic Sourcing Optimization
    IT 17 034 Examensarbete 15 hp Juni 2017 Quadratic Programming Models in Strategic Sourcing Optimization Daniel Ahlbom Institutionen för informationsteknologi Department of Information Technology Abstract Quadratic Programming Models in Strategic Sourcing Optimization Daniel Ahlbom Teknisk- naturvetenskaplig fakultet UTH-enheten Strategic sourcing allows for optimizing purchases on a large scale. Depending on the requirements of the client and the offers provided for Besöksadress: them, finding an optimal or even a near-optimal solution can become Ångströmlaboratoriet Lägerhyddsvägen 1 computationally hard. Mixed integer programming (MIP), where the Hus 4, Plan 0 problem is modeled as a set of linear expressions with an objective function for which an optimal solution results in a minimum objective Postadress: value, is particularly suitable for finding competitive results. Box 536 751 21 Uppsala However, given the research and improvements continually being made for quadratic programming (QP), which allows for objective functions with Telefon: quadratic expressions as well, comparing runtimes and objective values 018 – 471 30 03 for finding optimal and approximate solutions is advised: for hard Telefax: problems, applying the correct methods may decrease runtimes by several 018 – 471 30 00 orders of magnitude. In this report, comparisons between MIP and QP models used in four different problems with three different solvers Hemsida: were made, measuring both optimization and approximation performance in http://www.teknat.uu.se/student terms of runtimes and objective values. Experiments showed that while QP holds an advantage over MIP in some cases, it is not consistently efficient enough to provide a significant improvement in comparison with, for example, using a different solver.
    [Show full text]